Method for regulating the temperature of the coolant in an internal combustion engine using an electrically operated coolant pump

ABSTRACT

A method of regulating the temperature of the coolant circuit in an internal combustion engine is described, using an electrically operated coolant pump whose speed regulates or controls the cooling capacity. A great excess of heat can be dissipated and rapid heating of the internal combustion engine can be achieved by using an additional bypass line having corresponding thermostatic valves.

FIELD OF THE INVENTION

The present invention relates to a method of regulating the temperatureof a coolant in an internal combustion engine which is connected to aradiator by at least one forward and return line and to a coolant pump.

BACKGROUND INFORMATION

Methods and equipment for cooling the coolant in an internal combustionengine are already known in principle. For example, German Patent No. 3705 232 describes a method of regulating the temperature of the coolantwhere a sensor operates a motor actuator as a function of individualengine map characteristics, e.g., rpm and/or engine load, to open orclose a bypass valve or the like to achieve a predetermined temperaturein the engine coolant circuit. To control the motor actuator, the sensoris heated by a heating device according to the given characteristicdata, so it can deliver a suitable signal to the motor actuator. Such adevice seems relatively expensive in terms of energy required, becausethe drive motor for the coolant pump runs constantly, regardless ofwhether a small amount of waste heat needs to be removed when theinternal combustion engine is idling or a large amount when the engineis running.

SUMMARY OF THE INVENTION

The method according to the present invention for regulating thetemperature of a coolant in an internal combustion engine, however, hasthe advantage that the speed of the coolant pump is itself regulated orcontrolled so that its speed corresponds only to the heat to bedissipated.

It is especially advantageous for the speed control to be determinedfrom the temperature difference between the setpoint and theinstantaneous temperature of the internal combustion engine, becausesignificant operating states of the engine are detected in thistemperature difference.

By preselecting the setpoint temperature as a function of time, thewarmup phase of the engine can be controlled easily in an advantageousmanner.

It seems especially advantageous to select the setpoint temperature onthe basis of a time table, because an especially easy adjustment todifferent types of engines and their coolant circuits is possible inthis way.

The control signal for the coolant pump can be regulated especiallyeasily and advantageously by using a PID controller.

Another advantage is that in addition to controlling the coolant pump,other valves such as the thermostatic valve, the heating valve or anengine fan can also be controlled to optimize the cooling capacity. Thisadditional influence on the coolant circuit can be used either to makethe engine warm up more quickly in the cold start phase or to removeexcess heat more rapidly at a high load and when the engine is turnedoff. This reduces exhaust emissions and prevents overheating of theengine.

It also seems advantageous that a suitable display appears when theengine temperature is exceeded, allowing the driver to reactappropriately and thus prevent damage.

It is also advantageous that the parameters are linked in stages in themanner of fuzzy logic to guarantee optimal temperature conditions forthe internal combustion engine.

By linking the various parameters such as rpm, engine load, vehiclespeed and intake temperature or outside temperature, it is possible toform a control signal for the coolant pump which takes into account allthe operating conditions that occur.

GRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a coolant circuit of an internalcombustion engine.

FIG. 2 shows a block diagram of the temperature control.

DETAILED DESCRIPTION

In the schematic diagram of the coolant circuit in FIG. 1, internalcombustion engine 1 is connected to a radiator 4 via an electricallyoperated coolant pump M and a thermostatic valve 2 by a forward line 7.At a suitable location, a forward sensor 6 a for detecting the forwardtemperature is installed on the forward line 7. In addition, theinstantaneous temperature of internal combustion engine 1 is measuredwith a temperature sensor 6. A return line 8 connects radiator 4 to thecoolant circuit of internal combustion engine 1 via a heating valve 3.Heating valve 3 is also connected to heater 5 of the passengercompartment. Likewise, thermostatic valve 2 is connected to return line8 through another valve and bypass line 9. For the sake of thoroughness,it should also be pointed out that the radiator is thermally connectedto one or more engine fans 10, where engine fan 10 may be designed formultiple speeds. According to FIG. 1, valves 2, 3 are designed as 3-wayvalves.

The functioning of this arrangement is explained in greater detail belowon the basis of the block diagram in FIG. 2. Item 11 is a setpointgenerator for the engine temperature, which is preselected as a functionof time or in the form of a table, for example. The instantaneous enginetemperature measured with temperature sensor 6 is processed in asuitable manner in block 12 and sent to summing unit 14. Thedifferential signal between setpoint generator 11 and block 12 forms acorrection quantity for the control signal for coolant pump M in block13. Then the PID controller signal of block 13 is added up in summingunit 15, taking into account other parameters supplied by block 16 forcontrol of the coolant pump. The other parameters include, for example,values for the engine rpm, the instantaneous engine load of the internalcombustion engine, vehicle speed, intake temperature or outsidetemperature, the engine temperature itself and/or the on-board voltage.This is represented symbolically by the parallel arrows at block 16.After linking the signals to the PID controller signal, the controlsignal for coolant pump M is formed in block 15. Depending on thisvalue, coolant pump M runs at a corresponding speed, thus causing acorresponding change in rate of coolant flow in forward line 7 and/orreturn line 8. If this control algorithm is not sufficient to adjust thesetpoint temperature for the engine, thermostatic valve 2 ormultiple-speed engine fan 10 is controlled or a warning display on thedashboard is activated in block 17 after a suitable analysis of theinstantaneous engine temperature (block 12) and the control signal forthe coolant pump. These elements are represented symbolically by theparallel output arrows of block 17.

Since special functions for control of coolant pump M may be needed formaintenance jobs or in the workshop, a device is provided in block 18 toallow a separate drive for coolant pump M. This block 18 thereforecontains suitable devices, e.g., for connecting a workshop tester whichdrives coolant pump M in filling and venting the cooling system. As analternative, the internal combustion engine can also be warmed up overthis line by using an auxiliary heater (not shown in the figure).Furthermore, operation of coolant pump M to prevent overheating afterturning off a hot internal combustion engine 1 can also be controlledover this line.

The blocks shown in FIG. 2 are designed as known components (e.g., PIDcontrollers, temperature sensors, etc.). The simplest linkage is throughan appropriate program.

Rules for adjusting the cooling capacity can be taken from Tables 1 and2. For example, if engine temperature tmot is >85° C. according to Table1, and if the forward temperature of coolant pump tvkmp is >90%, thenthermostatic valve 2 is operated, for example, to coolant over forwardline 7 to radiator 4 and then return it over return line 8. If there isa further increase in engine temperature tmot, and if it is >95° C. atthe same relative capacity of coolant pump M, then fan speed 1 isactivated. Then when the engine temperature rises further to more than100° C., fan speed 2 is activated. When the temperature of the internalcombustion engine increases further to above 110° C., the “overheating”warning is displayed on the dashboard.

Table 2 shows as an example the measures taken to reduce the coolingcapacity. If engine temperature tmot is <105° C. and the coolingcapacity is <80%, then the “overheating” warning is deactivated.Accordingly, when the engine temperature is <97° C. and the coolingcapacity is <80% or <60%, fan speeds 2 and 1, respectively, are turnedoff. If the temperature drops further, e.g., tmot <83° C. and a coolingcapacity <40%, valve 2 is switched so that radiator 4 is turned off andbypass line 9 handles the return flow to internal combustion engine 1.Thermostatic valve 2 also closes at temperatures <75° C., so the engineheats up rapidly according to the given temperature curve. Rapid heatingof internal combustion engine 1 has the advantage that the noxiousexhaust during the warmup phase can be reduced as rapidly as possible.

Since commercially available electronic components (ICs) are often usedfor control operations, a further embodiment of the present inventionprovides for this control to be established according to the principlesof fuzzy logic.

TABLE 1 The following measures can be taken to increase coolingcapacity: tmot > 85° C. & tvkmp > 90% then thermostatic valve opentmot > 95° C. & tvkmp > 90% then fan speed 1 on tmot > 100° C. & tvkmp >90% then fan speed 2 on tmot > 110° C. & tvkmp > 90% then “overheating”warning on

TABLE 2 The following measures can be taken to reduce cooling capacity:tmot < 105° C. & tvkmp > 80% then “overheating” warning Off tmot < 97°C. & tvkmp < 80% then fan speed 2 off tmot < 97° C. & tvkmp < 60%then fan speed 1 off tmot < 83° C. & tvkmp < 40% then thermostatic valveclosed tmot < 75° C. then thermostatic valve closed

What is claimed is:
 1. A method of regulating a temperature of a coolantin an internal combustion engine connected to a radiator by at least oneforward line and a return line and having a thermostatic valve, a bypassline arranged between the at least one forward line and the return line,and a coolant pump, comprising the steps of: electrically driving thecoolant pump; and causing a control to select a speed for the coolantpump, as a function of at least one of at least one of engine parametersand ambient parameters, an actual engine temperature, a setpoint enginetemperature, and load parameters.
 2. The method according to claim 1,wherein: the at least one of the engine parameters and the ambientparameters corresponds to an engine rpm.
 3. The method according toclaim 1, further comprising the step of: determining the speed for thecoolant pump at least by a temperature difference between the setpointengine temperature and an instantaneous temperature of the internalcombustion engine.
 4. The method according to claim 1, furthercomprising the step of: selecting the setpoint engine temperature as afunction of time after a start of the internal combustion engine.
 5. Themethod according to claim 3, further comprising the step of: specifyingthe setpoint engine temperature based on a time table after a start ofthe internal combustion engine.
 6. The method according to claim 1,wherein: the control includes a controller with PID characteristics. 7.The method according to claim 1, further comprising the step of: causinga control signal for the coolant pump to control the thermostatic valve.8. The method according to claim 1, further comprising the step of:causing a control signal of the coolant pump to control an engine fan.9. The method according to claim 1, further comprising the step of:delivering one of a visual warning signal and an acoustic warning signalwhen at least one of the actual engine temperature and a forwardtemperature exceeds a level.
 10. The method according to claim 1,further comprising the step of: selecting at least one additionaldecision threshold for the actual engine temperature and a coolantcapacity of the coolant pump.
 11. The method according to claim 10,further comprising the step of: switching one of the thermostatic valve,an engine fan speed, and a warning indicator in accordance with the atleast one additional decision threshold.
 12. A method of regulating atemperature of a coolant in an internal combustion engine connected to aradiator by at least one forward line and a return line and having athermostat valve, a bypass line arranged between the at least oneforward line and the return line, and a coolant pump, comprising thesteps of: electrically driving the coolant pump; and causing a controlto select a speed for the coolant pump as a function of at least one ofengine parameters and ambient parameters.
 13. The method according toclaim 12, wherein the at least one of the engine parameters and theambient parameters includes at least one of an engine rpm, an actualengine temperature, a setpoint engine temperature and a load parameter.14. The method according to claim 12, further comprising the step ofdetermining the speed for the coolant pump at least in accordance with atemperature difference between the setpoint engine temperature and aninstantaneous temperature of the internal combustion engine.
 15. Themethod according to claim 12, further comprising the step of selectingthe setpoint engine temperature as a function of time after a start ofthe internal combustion engine.
 16. The method according to claim 14,further comprising the step of specifying the setpoint enginetemperature based on a time table after a start of the internalcombustion engine.
 17. The method according to claim 12, wherein thecontrol includes a controller with PID characteristics.
 18. The methodaccording to claim 12, further comprising the step of causing a controlsignal for the coolant pump to control the thermostatic valve.
 19. Themethod according to claim 12, further comprising the step of deliveringone of a visual warning signal and an acoustic warning signal when atleast one of an actual engine temperature and a forward temperatureexceeds a level.
 20. The method according to claim 12, furthercomprising the step of selecting at least one additional decisionthreshold for the actual engine temperature and a coolant capacity ofthe coolant pump.
 21. The method according to claim 12, furthercomprising the step of switching one of the thermostatic valve, anengine fan speed, and a warning indicator in accordance with the atleast one additional decision threshold.